Volume 59, Number 5, September 2002
|Page(s)||754 - 760|
|Section||Condensed matter: electronic structure, electrical, magnetic, and optical properties|
|Published online||01 September 2002|
On the consequences of the uncertainty principle on the superconducting fluctuations well inside the normal state
Laboratorio de Baixas Temperaturas e
Superconductividade Departamento de Física da Materia
Condensada Universidade de Santiago de Compostela -
Santiago de Compostela, E-15782, Spain
Accepted: 5 June 2002
We first argue that the collective behaviour of the Cooper pairs created by thermal fluctuations well above the superconducting transition temperature, Tc, is dominated by the uncertainty principle which, in particular, leads to a well-defined temperature, Tc, above which the superconducting coherence vanishes. On the grounds of the BCS approach, the corresponding reduced temperature, , is estimated to be around 0.55, i.e., above coherent Cooper pairs cannot exist. The implications of these proposals on the superfluid density are then examined using the Gaussian-Ginzburg-Landau approximation. Then we present new measurements of the thermal fluctuation effects on the electrical conductivity and on the magnetization in different low- and high-Tc superconductors with different dopings which are in excellent agreement with these proposals and that demonstrate the universality of .
PACS: 74.20.-z – Theories and models of superconducting state / 74.20.De – Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) / 74.40.+k – Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.)
© EDP Sciences, 2002
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